1. Field of the Invention
This invention relates to reinforced poly(phenylene ether)polyester compositions which exhibit enhanced properties, such as improved heat resistance and flow.
2. Brief Description of the Related Art
Poly(phenylene ether) resins (referred to hereafter as "PPE") are commercially attractive materials because of their unique combination of properties, for example, high strength, dimensional and hydrolyric stability, and dielectric properties. Furthermore, the combination of these resins with polyester resins into compatibilized blends can result in additional overall properties such as improved chemical resistance necessary for many automotive applications. For example, PPE-polyester blends compatibilized with an effective amount of a polycarbonate resin can be found in U.S. Pat. Nos. 4,831,087, 4,927,881 and 4,978,715, which are all incorporated herein by reference.
The overall physical properties of reinforced PPE-polyester blends would make them attractive for a variety of articles in the automotive market except that many of these articles are subjected to end-use temperatures in excess of 250.degree. F., the upper temperature capability of these blends.
Moreover, many of these same articles are preferentially produced using conversion techniques such as injection molding. Some of the most desirable applications, for example, instrument panels have very long flow lengths and therefore require resins that have very low viscosities in order to completely fill the molding tools. Reinforced PPE-polyester blends have inadequate flow properties at the processing temperatures that are needed to minimize the thermal degradation of the resins. Increasing the processing temperature to very high temperatures in order to reduce viscosity of the blends results in brittle parts and many surface imperfections in the final part, both of which are unacceptable.
Additives that increase the flow of other resin compositions are generally not usefuls in PPE-polyester compositions as they typically act to improve the flow by lowering the molecular weight of one of the components of the composition, or they result in significant loss in the heat resistance of the composition. These results are unsatisfactory. Thus, one of the goals of the present invention is to improve the flow of PPE-polyester compositions while retaining or enhancing the physical properties.
It is therefore apparent that a need continues to exist for reinforced PPE-polyester compositions that have improved heat distortion temperature and improved flow yet retain the other attractive physical properties.